This invention relates to a method and an apparatus for measuring the amount of air bubbles contained in incompressible liquid, and particularly to a method and an apparatus for measuring the amount of air bubbles mixed in incompressible liquid, in which the liquid to be measured containing air bubbles is introduced in a closed space and is then twice pressed under different pressures to compress the air bubbles in the liquid in order to provide two optional and different volumes of liquid, and the pressures of the two liquids having different pressures are measured by a pressure gage to determine the amount of air bubbles.
For instance, when a polyurethan resin is molded, air is preliminarily mixed with the liquid material. However, it is very difficult to precisely measure the amount of the mixed air.
Prior to the completion of this invention, the inventor had experimentally tried to measure the amount of the air bubbles contained in liquid to be measured, in such a way that a predetermined pressure was applied to the liquid containing air bubbles and the pressure was then released therefrom to move a piston of a cylinder or the like upward due to the stored energy, i.e. the pressure of the compressed air bubbles and then the displacement of the piston was measured. The inventor found as the result of the experiment that an exact measurement of the amount of air bubbles can not be effected in this way, because a high pressure of the air bubbles, enough to raise the piston, can not be obtained due to the large mechanical resistance of the piston and the cylinder.